The present invention relates to an eyeglass lens processing apparatus for processing a peripheral edge of an eyeglass lens and a lens-fixing cup.
In processing the peripheral edge of an eyeglass lens, the peripheral edge of an eyeglass lens held by two lens chuck axes of the eyeglass lens processing apparatus is roughed by a roughing grindstone and thereafter finished by e.g. a finishing grindstone (see for example, U.S. Pat. No. 6,283,826 (JP-A-11-333684)). When the lens is held by the two lens chuck axes, first, a cup serving as a processing jig is fixed to the surface of the lens using a blocker. Thereafter, a base of the cup is mounted in a cup holder of the one lens chuck axis and the lens is held by a lens presser of the other lens chuck axis.
The lens during the processing undergoes load due to the reaction force and rotating force by the grinding stone. Considering this fact, in processing the lens with a large target lens shape, in order to ensure the holding force by chucking to the utmost, a large diameter cup with a large attaching area is adopted.
In recent years, the design of an eyeglass frame has been diversified and the processing of a lens with a narrow vertical width has been increased. In processing the lens with the target lens shape having a narrow vertical width, if an ordinary cup with a large diameter may interfere with a processing tool, a small diameter cup with a small vertical size of the plane to be attached to the lens is adopted (see, for example, U.S. Pat. No. 6,241,577 (JP-A-10-249692)).
However, in chucking, the small diameter cup provides a holding force smaller than that of the large diameter cup. Owing to this, particularly, in roughing the peripheral edge of a unprocessed lens with a large diameter, a rotary moment load applied to the lens chuck axes increases so that axis deviation is likely to occur. Further, in the case of the lens coated with a water-repellent substance in which water or oil is not prone to be deposited, this problem will become more conspicuous.